Urine Pregnancy Test

Urine Pregnancy Test

Alternate Names

Definition

This test detects the level in the urine of the pregnancy hormone known as human chorionic gonadotropin (HCG).

Who is a candidate for the test?

HCG is a hormone that is produced by the placenta. It appears in the blood and urine within 10 days of fertilization of the egg by the sperm (conception).

After the unborn baby begins growing into an unborn baby, he or she implants, or attaches, to the inside of the uterus or other structure inside the mother, the levels of HCG rise rapidly. The levels continue to increase throughout the first trimester (3 months) of pregnancy and reach a peak 60 to 80 days after the unborn baby implants.

HCG is thought to be important in converting the normal corpus luteum into the corpus luteum of pregnancy. The corpus luteum is a hormone-secreting structure that grows on the surface of the ovary after ovulation takes place.

In pregnancy, functions of the corpus luteum include:

promoting the growth of the unborn child through the 12th week of pregnancy.

stimulating the development of unborn child's sex organs.

promoting the synthesis of male hormones by the unborn boy's testes. Interestingly, an elevated level of HCG in men may indicate the presence of a testicular tumor.

Because HCG is produced by the placenta, the presence of HCG in a woman's blood almost always indicates that she is pregnant. HCG is produced whether the unborn baby implants in the uterus (the normal situation) or outside the uterus in the fallopian tube or on another structure in the abdomen or pelvis (an ectopic pregnancy).

An HCG test is usually done to confirm or rule out pregnancy. Women of childbearing age who have been having sex should be evaluated with some type of HCG test if they are having the following symptoms:

delayed menstrual period

breast tenderness

pelvic pain

irregular vaginal spotting or bleeding

nausea or vomiting

How is the test performed?

The person supplies a urine sample, ideally from the first urination of the morning. This urine tends to be highly concentrated.

The sample is sent to the lab and analyzed for the presence of HCG. The hormone is measured in terms of quantity per cubic centimeter of urine. The hormone is detected with a test that uses specialized antibodies that clot with the HCG molecules. When this happens, the test is deemed positive. It is this reaction that makes the test strip turn color in over-the-counter pregnancy tests

A version of the test can also be performed on a blood specimen. The blood test turns positive earlier in the pregnancy, but because it requires a blood draw, it is not convenient for home use.

What is involved in preparation for the test?

No special preparation is necessary for this test.

What do the test results mean?

Usually, a positive test means that the woman is pregnant. The test cannot distinguish whether the pregnancy is normal or abnormal. Certain tumors of the placenta also produce HCG and therefore turn the test positive even when the woman is not pregnant.

Incorrect results, which are called false-positive or false-negative, results may occur with:

blood or protein in the urine.

use of phenothiazines, such as prochlorperazine (i.e., Thorazine) or promethazine (i.e., Phenergan).

use of penicillin.

use of methadone (i.e., Dolophine, Mehadose).

urinary tract infection.

hepatitis.

Other potential diagnoses that may mimic pregnancy but have negative HCG results include:

ovarian cysts.

bleeding without ovulation.

dysfunctional uterine bleeding, which is abnormal bleeding from the uterus that occurs outside of the normal menstrual flow.

pelvic inflammatory disease (PID), which is widespread infection of the ovaries, tubes, and other reproductive organs.

polycystic ovary disease, which is an endocrine disorder causing multiple cysts on the ovaries.